When designing racing vehicles, a key factor that plays a significant role in the performance of a vehicle is its weight. Decreasing the weight of a racing vehicle, even by a small amount, can result in improved acceleration and a greater overall top speed. One portion of racing vehicles that is often targeted for use of lighter components is the axles thereof, primarily due to the fact that conventional axles are formed from heavy, steel, tubular members.
For example, a typical rear axle of a racing vehicle (e.g., a drive axle) will include one or multiple steel tubulars, having varying points of thickness along their length, for providing desirable suspension characteristics and impact resistance. A hub is positioned at the outer edge of each tubular, to which a wheel is secured, while some manner of engagement with the drive system (e.g., gears, splines, etc.) are formed on the inner ends of each tubular. It is possible for an entire axle assembly (e.g., the hub, shaft, and a splined connector) to be machined from a single piece of steel, though it is also possible to weld or otherwise connect separate hub and connector components to a shaft.
In addition to the disadvantages inherent in their weight, steel components can be readily damaged and/or deformed, especially if subjected to a significant side impact. Due to its generally high modulus of elasticity, a steel axle that is bent through an impact will remain warped, requiring replacement.
To attempt to address the drawbacks of conventional steel materials, use of alternate materials has been explored, including various plastics and composites, as well as alternate metals. For example, use of an axle shaft assembly formed wholly from titanium has been attempted; however, due to the fact that titanium parts cannot be readily welded and/or attached to adjacent parts, such an assembly is expensive to produce, requiring the machining of a single piece of titanium that is large enough to form both an integral hub and shaft. Additionally, while an axle assembly formed wholly from titanium is lighter and more flexible than steel counterparts, titanium splines are prone to breakage and rapid wear, even when provided with wear resistant coatings and surface treatments. Further, titanium hub connections are significantly more complex and expensive than typical steel counterparts.
A need exists for axle shaft assemblies and methods that combine materials having low and high moduli of elasticity to provide desirable weight, suspension, impact resistance, and durability characteristics to a vehicle, while enabling a higher fatigue life.
A need also exists for axle shaft assemblies and methods that incorporate modular components.
Embodiments usable within the scope of the present disclosure meet these needs.